#!/usr/bin/env python3
#
# process-reboot-cause
#
# Program designed to read the previous reboot-cause files, log the last previous reboot-cause.
# And read the saved reboot-cause history files and save the reboot cause in the state-db.
#

try:
    import json
    import os
    import pwd
    import sys

    from swsscommon import swsscommon
    from sonic_py_common import logger
except ImportError as err:
    raise ImportError("%s - required module not found" % str(err))

VERSION = "1.0"

SYSLOG_IDENTIFIER = "process-reboot-cause"

REBOOT_CAUSE_DIR = "/host/reboot-cause/"
REBOOT_CAUSE_HISTORY_DIR = "/host/reboot-cause/history/"
PREVIOUS_REBOOT_CAUSE_FILE = os.path.join(REBOOT_CAUSE_DIR, "previous-reboot-cause.json")
USER_ISSUED_REBOOT_CAUSE_REGEX ="User issued \'{}\' command [User: {}, Time: {}]"

REBOOT_CAUSE_UNKNOWN = "Unknown"
REBOOT_CAUSE_TABLE_NAME = "REBOOT_CAUSE"

REDIS_HOSTIP = "127.0.0.1"
state_db = None

# Global logger class instance
sonic_logger = logger.Logger(SYSLOG_IDENTIFIER)


# ============================= Functions =============================
def read_reboot_cause_files_and_save_state_db():
    # Connect State DB
    state_db = swsscommon.SonicV2Connector(host=REDIS_HOSTIP)
    state_db.connect(state_db.STATE_DB)

    # Sort the previous reboot cause files by creation time
    REBOOT_FILE_LIST = [os.path.join(REBOOT_CAUSE_HISTORY_DIR, i) for i in os.listdir(REBOOT_CAUSE_HISTORY_DIR)]
    TIME_SORTED_FULL_REBOOT_FILE_LIST = sorted(REBOOT_FILE_LIST, key=os.path.getmtime, reverse=True)

    data = []
    # Read each sorted previous reboot cause file and update the state db with previous reboot cause information
    for i in range(min(10, len(TIME_SORTED_FULL_REBOOT_FILE_LIST))):
        x = TIME_SORTED_FULL_REBOOT_FILE_LIST[i]
        if os.path.isfile(x):
            with open(x, "r") as cause_file:
                data = json.load(cause_file)
                _hash = '{}|{}'.format(REBOOT_CAUSE_TABLE_NAME, data['gen_time'])
                state_db.set(state_db.STATE_DB, _hash, 'cause', data['cause'])
                state_db.set(state_db.STATE_DB, _hash, 'time', data['time'])
                state_db.set(state_db.STATE_DB, _hash, 'user', data['user'])
                state_db.set(state_db.STATE_DB, _hash, 'comment', data['comment'])

    if len(TIME_SORTED_FULL_REBOOT_FILE_LIST) > 10:
        for i in range(len(TIME_SORTED_FULL_REBOOT_FILE_LIST)):
            if i >= 10:
                x = TIME_SORTED_FULL_REBOOT_FILE_LIST[i]
                os.remove(x)


def main():
    # Configure logger to log all messages INFO level and higher
    sonic_logger.set_min_log_priority_info()

    sonic_logger.log_info("Starting up...")

    if not os.geteuid() == 0:
        sonic_logger.log_error("User {} does not have permission to execute".format(pwd.getpwuid(os.getuid()).pw_name))
        sys.exit("This utility must be run as root")

    # Set a default previous reboot cause
    previous_reboot_cause = REBOOT_CAUSE_UNKNOWN

    # Read the most recent reboot cause file and log data to syslog
    if os.path.exists(PREVIOUS_REBOOT_CAUSE_FILE):
        with open(PREVIOUS_REBOOT_CAUSE_FILE, "r") as last_cause_file:
            data = json.load(last_cause_file)
            if data['user']:
                previous_reboot_cause = USER_ISSUED_REBOOT_CAUSE_REGEX.format(data['cause'], data['user'], data['time'])
            else:
                previous_reboot_cause = "{}".format(data['cause'])

    # Log the last reboot cause to the syslog
    sonic_logger.log_info("Previous reboot cause: {}".format(previous_reboot_cause))

    if os.path.exists(REBOOT_CAUSE_HISTORY_DIR):
        # Read the previous reboot cause from saved reboot-cause files and save the previous reboot cause upto 10 entry to the state db
        read_reboot_cause_files_and_save_state_db()


if __name__ == "__main__":
    main()
